Physical simulation experiment system for vapor-liquid multiphase seepage in underground gas storage facility in depleted gas reservoir

Abstract

Disclosed is a physical simulation experiment system for vapor-liquid multiphase seepage in an underground gas storage facility in a depleted gas reservoir, including: a rock sample sealing, heating, and insulation system, a triaxial stress and confining pressure loading system, an oil-gas-water injection and pore pressure supply system, a vapor-liquid-solid three-phase separation and measurement system, an optical micro/nanofiber gas detection and monitoring system, a distributed fiber optic sensing system, and a gas supply and leakage alarm system, where the rock sample sealing, heating, and insulation system is used for accommodating and heating a rock sample; and the oil-gas-water injection and pore pressure supply system performs oil-gas-water injection into the rock sample and pore pressure maintenance. The present application aims to overcome the bottleneck problem of evaluating the dynamic sealing integrity of underground gas storage under alternating loads caused by injection and withdrawal.

What is claimed is: 
     
         1 . A physical simulation experiment system for vapor-liquid multiphase seepage in an underground gas storage (UGS) facility in a depleted gas reservoir, comprising:
 a rock sample sealing, heating, and insulation system, comprising a rock sample sealing unit for accommodating a rock sample and a heating and insulation unit for heating the rock sample, wherein the rock sample sealing unit comprises a main pressure chamber, a rock sample rubber sleeve, and loading plates; the main pressure chamber has a central cavity for accommodating the rock sample and providing a confining pressure environment for the rock sample; the rock sample rubber sleeve is fitted around an outer wall of the rock sample to seal the rock sample; and the loading plates are arranged around the rock sample respectively and press against the rock sample rubber sleeve on the outer wall of the rock sample;   a triaxial stress and confining pressure loading system, comprising a triaxial stress loading unit for applying triaxial stress to the rock sample and a confining pressure loading unit for applying a confining pressure to the rock sample, wherein the triaxial stress loading unit comprises loading cylinders positioned around the rock sample, a servo loading pump that provides a power source for the loading cylinders, a servo oil source that offers pre-pressurization for axial loading, a servo valve that controls a hydraulic pressure of the loading cylinders, a directional control valve that controls a piston movement direction of the loading cylinders, a displacement sensor that controls displacement of the loading cylinders, and an air compressor that supplies a low-pressure power to reset pistons of the loading cylinders; loading heads of the loading cylinders press against the loading plates around the rock sample respectively; and the confining pressure loading unit comprises a high-precision constant flow/pressure pump connected to the main pressure chamber via a pipeline to provide a constant pressure within the main pressure chamber, thereby applying the confining pressure to the rock sample;   an oil-gas-water injection and pore pressure supply system connected to an inlet end of the rock sample via a pipeline, comprising a vapor-phase injection unit and a liquid-phase injection unit to perform oil-gas-water three-phase injection into the rock sample;   a vapor-liquid-solid three-phase separation and measurement system connected to an outlet end of the rock sample via a pipeline, comprising a back-pressure unit, a solid separation and measurement unit, and a vapor-liquid separation and measurement unit;   an optical micro/nanofiber gas detection and monitoring system, configured to detect leakage of specified gases;   a distributed fiber optic sensing system, configured to monitor and record internal deformation and fracture initiation of the rock sample during a loading process; and   a gas supply and leakage alarm system, configured to provide safe and reliable centralized gas supply;   wherein the heating and insulation unit comprises:   heating rods embedded around an interior of the main pressure chamber to heat the main pressure chamber and transfer heat to the rock sample; and   a flexible insulation jacket wrapped around an exterior of the main pressure chamber to provide thermal insulation and temperature compensation for the main pressure chamber.   
     
     
         2 . The physical simulation experiment system for vapor-liquid multiphase seepage in the UGS facility in the depleted gas reservoir of  claim 1 , wherein the vapor-phase injection unit is connected to the rock sample via a pipeline and comprises a gas booster pump set connected via a pipeline for supplying a high-pressure gas at an input end, a high-pressure gas storage vessel for storing the high-pressure gas, an air compressor for supplying power to the gas booster pump set, a pneumatic pressure controller for controlling a gas pressure, and a gas flow controller for controlling a gas flow rate. 
     
     
         3 . The physical simulation experiment system for vapor-liquid multiphase seepage in the UGS facility in the depleted gas reservoir of  claim 2 , wherein the liquid-phase injection unit is connected to the rock sample via a pipeline and comprises a liquid constant-flow and constant-pressure pump and a piston container, both connected via a pipeline, and the piston container is configured to isolate a working fluid from an injected fluid. 
     
     
         4 . The physical simulation experiment system for vapor-liquid multiphase seepage in the UGS facility in the depleted gas reservoir of  claim 1 , wherein the back-pressure unit comprises a back-pressure pump, a back-pressure container, and a back-pressure valve, all connected via a pipeline; the solid separation and measurement unit is disposed between the outlet end of the rock sample and the back-pressure valve and comprises a solid collection and measurement container for separating solids; and the vapor-liquid separation and measurement unit is connected to the back-pressure valve and comprises a vapor-liquid separator for performing vapor-liquid separation on a fluid from the outlet end of the rock sample, wherein a separated gas is discharged through a top outlet of the vapor-liquid separator and passes through a drying tank to enter either a high-speed or low-speed gas flow meter for vapor-phase flow measurement, a separated liquid is discharged through a bottom outlet of the vapor-liquid separator and passes through an oil-water separation tube to enter either an oil-phase metering pump for oil-phase flow measurement or a water-phase metering pump for water-phase flow measurement, and an oil-water interface detector is arranged on the oil-water separation tube. 
     
     
         5 . The physical simulation experiment system for vapor-liquid multiphase seepage in the UGS facility in the depleted gas reservoir of  claim 1 , wherein the optical micro/nanofiber gas detection and monitoring system comprises a gas probe arranged inside the rock sample and a signal conditioner electrically connected to the gas probe. 
     
     
         6 . The physical simulation experiment system for vapor-liquid multiphase seepage in the UGS facility in the depleted gas reservoir of  claim 1 , wherein the distributed fiber optic sensing system comprises a light source, a coupler, a detector, and optical fibers, all connected electrically, and the optical fibers are embedded inside the rock sample. 
     
     
         7 . The physical simulation experiment system for vapor-liquid multiphase seepage in the UGS facility in the depleted gas reservoir of  claim 1 , wherein the gas supply and leakage alarm system comprises a gas cylinder rack for holding gas cylinders, an electromagnetic valve arranged on a gas cylinder outlet pipeline, and a gas monitor, temperature/pressure sensors, a video monitor, a central monitoring server, an alarm, ventilation equipment, and fire extinguishing equipment, all connected to the electromagnetic valve via wiring, and an electrostatic protection device is arranged in a gas cylinder storage room.